1. Field of the Invention
The claimed invention is directed to an epitaxial wafer and to a method for producing the epitaxial wafer.
2. Description of the Related Art
Epitaxial wafers comprise a silicon substrate wafer having a first side and a second side, and a silicon epitaxial layer deposited on the first side of the silicon substrate wafer. Such wafers are prepared by depositing the silicon epitaxial layer on the first side of the silicon substrate wafer by chemical vapor deposition (CVD). Epitaxial wafers are used for manufacturing semiconductor devices such as memory devices and microprocessors.
Miniaturization of electronic device structures like transistors is in progress and amplifies several problems. It becomes more likely that dislocations caused by stress fields will damage or even destroy electronic device structures.
Accordingly, attempts have been made to strengthen the epitaxial layer against dislocation nucleation and propagation. US 2010/0151692 A1 proposes to subject the epitaxial wafer to a heat treatment under a non-oxidizing atmosphere such that the oxygen concentration of the surface of the silicon epitaxial layer is set to 1.0×1017 to 12×1017 atoms/cm3. It is believed that raising the oxygen concentration in the epitaxial layer improves the resistance to dislocation generation.
Another problem concerns metallic impurities which have a detrimental effect on the functional integrity of electronic devices. Attempts have been made to keep such impurities away from electronic device structures by providing gettering sites which are sinks for metallic impurities. Recent developments require shifting such gettering sites closer to the electronic device structures in order to reduce the diffusion length which impurities have to cover in order to reach the gettering sites.
US 2006/0175613 A1 discloses a method comprising growing a gettering layer over a semiconductor substrate and forming an epitaxial layer over the gettering layer.